1. Field of the Invention
The present invention relates to a color balance measuring device for regulating color balance of a photographic printer in which images are exposed onto a photosensitive material.
2. Background of the Invention
When color images, which are recorded on negative film, are printed onto photographic paper by a photographic printer, it is necessary to precisely control the amount of exposure and color balance to produce high-quality photographic prints. As a result, various photographic printers have been designed to obtain optimal prints by operating the amount of exposure and the color balance to effect color correction.
Adjustment of color balance in a photographic printer is effected in the following way. A standard print (referred to hereinafter as a "bull's eye print") is formed by a standard negative film (hereinafter, "bull's eye negative"), in which a round image of a predetermined color is recorded on a central portion thereof, being printed onto photographic paper. The image which is recorded on the bull's eye negative is printed in advance at the appropriate conditions onto a photographic print (hereinafter, "reference print"). For both the bull's eye print and the reference print, the amount of blue, green and red light, which is irradiated from a light source and reflected, are measured by light-intercepting particles provided in a density measuring portion. By comparing the results of the measurement of the reference print and the bull's eye print, exposure conditions (amount of exposure, exposure time for each color) in the photographic printer can be set.
Further, in the density measuring portion, it is necessary to adjust the measuring error of the light-intercepting elements (this adjustment is referred to hereinafter as "calibration"). Calibration is effected by the density measuring portion which measure for each color the quantity of light reflected on a while reference plate.
In a photographic printer, the color balance measuring device may be disposed at the operating panel. Color correction is effected by inserting the white reference plate, the bull's eye print, and the reference print into the color balance measuring device, and measuring the color balances thereof.
In a regular photographic printer, it is necessary to effect this color balance adjustment before beginning daily operation. Color balance adjustment is also effected after parts are changed, photographic paper is changed, developing processing liquids are replaced, and the like occurs at the exposure portion of the photographic printer.
However, in effecting calibration and color balance measurement, the white reference plate, the reference print and the bull's eye print must be tightly fit at the density measuring portion. Operation thereby becomes complex and troublesome. Moreover, in order to facilitate this operation, the density measuring portion is disposed in the transport path of the photographic prints. Therefore, the density measuring portion may contact the surfaces of the photographic prints. The surfaces of the photographic prints may be damaged, which lowers the quality of the final prints.